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<?php /** * http://stackoverflow.com/questions/9262109/php-simplest-two-way-encryption/30189841#30189841 * * This is not safe to use */ class UnsafeCrypto { const METHOD = 'aes-256-ctr'; /** * Encrypts (but does not authenticate) a message * * @param string $message - plaintext message * @param string $key - encryption key (raw binary expected) * @param boolean $encode - set to TRUE to return a base64-encoded * @return string (raw binary) */ public static function encrypt($message, $key, $encode = false) { $nonceSize = openssl_cipher_iv_length(self::METHOD); $nonce = openssl_random_pseudo_bytes($nonceSize); $ciphertext = openssl_encrypt( $message, self::METHOD, $key, OPENSSL_RAW_DATA, $nonce ); // Now let's pack the IV and the ciphertext together // Naively, we can just concatenate if ($encode) { return base64_encode($nonce.$ciphertext); } return $nonce.$ciphertext; } /** * Decrypts (but does not verify) a message * * @param string $message - ciphertext message * @param string $key - encryption key (raw binary expected) * @param boolean $encoded - are we expecting an encoded string? * @return string */ public static function decrypt($message, $key, $encoded = false) { if ($encoded) { $message = base64_decode($message, true); if ($message === false) { throw new Exception('Encryption failure'); } } $nonceSize = openssl_cipher_iv_length(self::METHOD); $nonce = mb_substr($message, 0, $nonceSize, '8bit'); $ciphertext = mb_substr($message, $nonceSize, null, '8bit'); $plaintext = openssl_decrypt( $ciphertext, self::METHOD, $key, OPENSSL_RAW_DATA, $nonce ); return $plaintext; } } class SaferCrypto extends UnsafeCrypto { const HASH_ALGO = 'sha256'; /** * Encrypts then MACs a message * * @param string $message - plaintext message * @param string $key - encryption key (raw binary expected) * @param boolean $encode - set to TRUE to return a base64-encoded string * @return string (raw binary) */ public static function encrypt($message, $key, $encode = false) { list($encKey, $authKey) = self::splitKeys($key); // Pass to UnsafeCrypto::encrypt $ciphertext = parent::encrypt($message, $encKey); // Calculate a MAC of the IV and ciphertext $mac = hash_hmac(self::HASH_ALGO, $ciphertext, $authKey, true); if ($encode) { return base64_encode($mac.$ciphertext); } // Prepend MAC to the ciphertext and return to caller return $mac.$ciphertext; } /** * Decrypts a message (after verifying integrity) * * @param string $message - ciphertext message * @param string $key - encryption key (raw binary expected) * @param boolean $encoded - are we expecting an encoded string? * @return string (raw binary) */ public static function decrypt($message, $key, $encoded = false) { list($encKey, $authKey) = self::splitKeys($key); if ($encoded) { $message = base64_decode($message, true); if ($message === false) { throw new Exception('Encryption failure'); } } // Hash Size -- in case HASH_ALGO is changed $hs = mb_strlen(hash(self::HASH_ALGO, '', true), '8bit'); $mac = mb_substr($message, 0, $hs, '8bit'); $ciphertext = mb_substr($message, $hs, null, '8bit'); $calculated = hash_hmac( self::HASH_ALGO, $ciphertext, $authKey, true ); if (!self::hashEquals($mac, $calculated)) { throw new Exception('Encryption failure'); } // Pass to UnsafeCrypto::decrypt $plaintext = parent::decrypt($ciphertext, $encKey); return $plaintext; } /** * Splits a key into two separate keys; one for encryption * and the other for authenticaiton * * @param string $masterKey (raw binary) * @return array (two raw binary strings) */ protected static function splitKeys($masterKey) { // You really want to implement HKDF here instead! return [ hash_hmac(self::HASH_ALGO, 'ENCRYPTION', $masterKey, true), hash_hmac(self::HASH_ALGO, 'AUTHENTICATION', $masterKey, true) ]; } /** * Compare two strings without leaking timing information * * @param string $a * @param string $b * @return boolean */ protected static function hashEquals($a, $b) { if (function_exists('hash_equals')) { return hash_equals($a, $b); } $nonce = openssl_random_pseudo_bytes(32); return hash_hmac(self::HASH_ALGO, $a, $nonce) === hash_hmac(self::HASH_ALGO, $b, $nonce); } } $message = 'Ready your ammunition; we attack at dawn.'; $key = hex2bin('000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f'); $encrypted = SaferCrypto::encrypt($message, $key, true); $decrypted = SaferCrypto::decrypt($encrypted, $key, true); var_dump($encrypted, $decrypted);